Hi all. On my 20 long I am having problems keeping it warm through the night. Temps were 75-76 during the day and dipping to 72 by morning. So I purchased a 50w heater and set it to 78. Well during the day it is fine but still at night it drops to 72. So my question would be is the 50w not enough. I am thinking not b/c its not doing the job right. What are my options? Bigger heater??